Even if someone has a long history of winning stock picks, it doesn't mean he will have continued success. This US News article
shows an example of this with this year's performance of Berkshire Hathaway, Warren Buffett's company.
The author provides the following bit of wisdom:
Your focus on stock picking, mutual fund manager picking, and market timing is a classic case of having your eye on the wrong ball,
He's in the index fund camp so he still thinks long-term stock investing makes sense as long as it's part of a balance diversified portfolio.